U.S. theme park operator SeaWorld Entertainment admitted Thursday that it had sent an employee undercover to infiltrate and spy on the animal rights group, People for the Ethical Treatment of Animals (PETA). The company would no longer use such practices, SeaWorld CEO Joel Manby said.

In July last year, PETA had accused a human resource employee of SeaWorld, Paul McComb, of posing as an animal rights activist and trying to incite violence among peaceful protesters.

SeaWorld’s board has “directed that the company’s management team end a practice in which certain employees posed as animal-rights activists,” Manby wrote in a statement Thursday. He added that Paul McComb had returned to work at SeaWorld but in a different position.

SeaWorld said it used to ask certain employees to infiltrate animal rights organizations in order to “maintain the safety and security of company employees, customers and animals in the face of credible threats that the company had received.”

SeaWorld has come under severe criticism after the release of a 2013 documentary, “Blackfish” that detailed the treatment of killer whales used in shows and the deaths of trainers by those whales. The killer whales were once the park's main attraction.

In a statement Thursday, PETA said that SeaWorld's acknowledgement was a confirmation that the company had disguised more than one person as activist.

Orlando-based SeaWorld also reported a loss for the fourth quarter Thursday that came in below Wall Street’s predictions. SeaWorld registered a rise in attendance at its parks but reported a loss of $11 million, or 13 cents a share, while analysts polled by Reuters projected the company to incur a loss of 10 cents per share, the Wall Street Journal reported.

Shares of the company plunged as much as 12 percent before closing 9.18 percent lower on the New York Stock Exchange Thursday.